I expect iPad and iPhone to represent approximately 69% of Apple’s quarterly revenue.

GM: 40.8%(AAPL guidance: 38.5%/Consensus: 40.4%)

Apple’s margin will likely decline sequentially from 3Q12 due to the iPhone 5 and continued iPad 2 sales. A key question facing AAPL in the near-term is the margin run rate. In 2011, Apple reported a 40.5% gross margin, which increased to approximately 44% in 2012. Looking at 2013, I expect margins to decline a few hundred basis points to 42% related to the iPad mini and ongoing costs related to the iPhone’s new form factor.

Mac growth is slowing as tablets and smartphones satisfy many consumers’ computing needs. I expect double-digit growth in portables, driven by back-to-school purchases, to be partially offset by a modest decline in desktop sales due to stale models.

iPad: 18.4 million(65% yoy growth)

I expect Apple to report record iPad sales for 4Q12. My iPad estimate assumes approximately 1.5 million iPads sold per week (including iPad 2 sales), which compares to the approximate 1.4 million weekly run rate last quarter. Supply/demand is in balance. Anecdotally, iPad 2 sales in education and business appear robust following the price cut, while lower component and manufacturing pricing should help limit drastic margin compression.

iPod: 6.1 million (8% yoy decline)

iPhone: 24.8 million (45% yoy growth)

My estimate reflects 7 million iPhone 5 units and approximately 18 million iPhone 4S units (and to a lesser extent iPhone 4 and 3GS). Apple is currently suffering from a supply/demand imbalance for iPhone 5, which will limit sales in the near-term (including 1Q13). Other unknowns include the iPhone 4S sales run-rate prior to the iPhone 5 introduction and iPhone 4S popularity following the price drop. My 18 million iPhone 4S estimate reflects the impact from consumers delaying iPhone purchases ahead of the iPhone 5 release. I am including a declining ASP due to robust iPhone 4S sales following the price drop (an observation partially derived from Verizon’s earnings which showed strong non-iPhone 5 sales, which I attribute to the price drop).

When Apple releases earnings on October 25, investors will focus on product ASPs and margin. Publicized iPhone 5 supply shortages and iPad mini rumors should go a long way in explaining any moderate misses in iPhone and iPad unit sales, respectively. Nevertheless, any evidence of continued margin weakness and declining ASP in iPad and iPhone may push observers to reduce forward earnings, which have a high sensitivity to margins. A 100 basis point change in margin corresponds to a 3% change in Apple quarterly EPS.